Thursday January 24 2008
Only one person in the study took vitamin E supplements
Vitamin E “helps older people move” is the headline in The Daily Telegraph. The newspaper report underneath says that “a diet rich in olive oil, nuts and green leafy vegetables could help slow physical decline in the elderly”.
The story is based on a study carried out in Italy, which looked at whether levels of micronutrients – particular vitamins and minerals – in the diet have a direct effect on the physical capabilities of older people. The results of the study show that low levels of vitamin E in the diet are linked to a decline in physical activity. The study has provided further evidence of the association between a healthy diet and fitness in older age; however, these results apply to people who have lower-than-normal vitamin E levels and therefore may not apply to healthy people who take extra vitamin E as a supplement.
Where did the story come from?
Dr Benedetta Bartali conducted the research along with colleagues from the Division of Nutritional Sciences, Cornell University, in New York, and other research institutions in the US and Italy. The study was supported by the Italian Ministry of Health and by multiple grants and contracts from US and Italian sources, including the US National Institute of Health. It was published in the (peer-reviewed) medical journal: The Journal of the American Medical Association.
What kind of scientific study was this?
This was a cohort study which used data collected from a population registry study in Italy to investigate whether low levels of vitamins and nutrients are linked to physical function in the elderly.
The researchers invited people aged 65 years and over, living in Tuscany, Italy, to take part in the study and 1,155 agreed. Of this group, 457 could not be included because they either demonstrated poor physical performance at the start of the study, or they didn’t have their initial physical performance measured. People for whom there was no follow-up data on file (for example from those who had died, emigrated or where the follow-up data had not been collected) were also excluded. This left 698 people with full data for analysis (60%).
The participants were asked questions about a range of issues including education, jobs, household composition, general health and functional state. They also completed a questionnaire designed to detect any depression or dementia. Participants were asked to specify their level of physical activity and this was subsequently classified into three groups: a sedentary group (people who were completely inactive or did light physical activity only, e.g. walking, for less than one hour a week); a light group who were physically active for two to four hours a week; and a moderate to intense group who did light physical activity for more than four hours a week or moderate physical activity (e.g. swimming) for one to two hours a week or more. The participants also completed a food questionnaire so that their intake of energy and nutrients could be calculated. A medical examination at the start of the study included height, weight and blood tests. The serum micronutrient concentration in the blood – i.e. the concentration of vitamin E, folic acid, vitamin B6, vitamin B12, vitamin D and iron – was tested and statistical models were used to relate this to the physical function as recorded in three annual follow-up visits.
At the follow-up visits, participants were given scores of 0–4 for their performance in three objective tests: the best time in two tests where they were asked to walk four metres; the total time taken to rise five times from seated to standing with hands folded; and a standing balance test. The total score for the three tests was added together to give the “Short Physical Performance Battery” score. This ranged from 0–12, with higher numbers representing better performance. The authors adjusted their results to take into account a number of baseline factors such as age, sex, physical activity (using the three groups), socio-economic status and weight.
What were the results of the study?
The average decline in the Short Physical Performance Battery score over the study period, for all participants, was 1.1 point. The analysis showed that of all the levels of micronutrients measured, only a low concentration of vitamin E was significantly associated with the subsequent decline in physical function.
Using other statistical tests, the researchers identified that the two strongest determinants of decline in physical function were being aged over 81 years, and the vitamin E concentration in participants aged 70–80 years. Only one person in the study was taking vitamin E supplements.
What conclusions did the researchers draw from these results?
The researchers say that these results provide “evidence that a low serum concentration of vitamin E is associated with subsequent decline in physical function among community-living older adults.” They have called for more clinical trials to investigate whether giving supplements to older people with low levels of vitamin E could reduce functional decline and the onset of disability.
What does the NHS Knowledge Service make of this study?
A large amount of data was collected in this study and the authors have presented some of the associations in this new publication, using three analytical approaches. They suggest three mechanisms which might account for the association of low vitamin E concentration and a decline in physical function. Potential limitations are acknowledged by the authors:
- The high loss of patients to follow-up may have introduced systematic errors into the analysis if the patients who were not included differed form the study population in important ways.
- The proportion of people taking vitamin supplements is different in different countries (4% in Italy compared with more than 50% in the United States), and the authors say that for this and other reasons the results from this study may not apply to other countries.
- When analysing a large amount of data retrospectively it’s not unusual to find one or two significant findings; however, even statistically significant findings can arise by chance.
The link shown in this study applies to people who have a lower-than-normal vitamin E concentration and the results will not necessarily apply to healthy people who take extra vitamin E as a supplement.
Sir Muir Gray adds...
Although I’m only 63, this looks like useful evidence to me. As there’s no evidence of harm it may be worth adding vitamin E to my daily vitamin D. However, I suspect what’s more important are the extra 3000 steps I take every day and the five minutes of tough exercise I take every day before leaving home.